Interpretive Summary: Contamination of pathogenic bacteria, e.g., E coli O157:H7 in foods may lead to serious public health concerns. To minimize possible outbreak of food poisoning by this bacteria, sensitive and rapid detection techniques are needed to call for proper treatments to intervene further distribution of contaminated foods. In the past years, we have developed a few specific cand sensitive methods which are capable to detect approximately 1 E. coli O157:H7 cell in one gram of hamburger. In all cases, pathogenic E. coli O157:H7 bacteria are first briefly enriched for about 4 to 6 hours and captured by magnetic beads that have been covered with proper antibodies. The beads together with captured E. coli are then concentrated by a magnet. After staining the nucleic acids in cells with fluorescent dyes, the bacteria may then be visualized and counted by an automated microscope. The bacteria may also be determined using a bioluminescence method in which hATP, a component of viable cells can be measured by the light emitted fro a reaction with firefly extracts. Alternatively, the bacteria may be tagged with proper enzymes that may be easily recognized. All three approaches mentioned above may be completed within a standard eight-hour shift. Thus, the information is useful for researcher and/or engineers to design reagent kits and automation processes to detect specific pathogenic bacteria in foods.

Technical Abstract:
There is a need for rapid, sensitive, and specific tests which researchers, farmers, processors, and retailers can use to verify that foods are safe to consume. Thus, we conducted research to develop new, or modify existing technologies to increase the speed, specificity and sensitivity of detecting food-borne pathogens to meet the needs of the food producers/processors and regulatory agencies. In this paper, we report a few developed biosensor approaches, including digital fluorescence imaging, ATP-bioluminescence and light-addressable potentiometric sensor (LAPS) to detect Escherichia coli O157:H7 in hamburger. Experimentally, we spiked the hamburger with the E. coli at a level of approximately1 CFU g-(1). The bacteria in the meat samples were then enriched at 37 degrees C for 5-6 h in novobiocin-containing EC medium. The bacteria were then captured and concentrated by the use of immunomagnetic beads. The captured bacteria were then quickly determined by the biosensor approaches mentioned above. All the processes could be completed within a standard factory 8-hour shift. In addition, the samples prepared for the LAPS approach, were stable for 48 h at 4 degrees C. This sample stability would permit samples collected from remote sites to be processed at a central location.